mm: Implement stack frame object validation
This creates per-architecture function arch_within_stack_frames() that
should validate if a given object is contained by a kernel stack frame.
Initial implementation is on x86.
This is based on code from PaX.
Signed-off-by: Kees Cook <keescook@chromium.org>
diff --git a/arch/Kconfig b/arch/Kconfig
index 1599629..ef86cde 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -424,6 +424,15 @@
endchoice
+config HAVE_ARCH_WITHIN_STACK_FRAMES
+ bool
+ help
+ An architecture should select this if it can walk the kernel stack
+ frames to determine if an object is part of either the arguments
+ or local variables (i.e. that it excludes saved return addresses,
+ and similar) by implementing an inline arch_within_stack_frames(),
+ which is used by CONFIG_HARDENED_USERCOPY.
+
config HAVE_CONTEXT_TRACKING
bool
help